Bump certifi in /doc in the pip group across 1 directory

Bumps the pip group with 1 update in the /doc directory: [certifi](https://github.com/certifi/python-certifi).


Updates `certifi` from 2020.12.5 to 2024.7.4
- [Commits](certifi/python-certifi@2020.12.05...2024.07.04)

---
updated-dependencies:
- dependency-name: certifi
  dependency-type: direct:production
  dependency-group: pip
...

Signed-off-by: dependabot[bot] <support@github.com>

doc/requirements.txt

@@ -9,7 +9,7 @@ matplotlib>=3.6.1
 docutils==0.18.1
 alabaster==0.7.12
 Babel==2.9.1
-certifi==2020.12.5
+certifi==2024.7.4
 chardet==4.0.0
 colorama==0.4.4
 idna==2.10